Mozilla plans to debut a "lockdown" feature in Firefox 3.6 to force third party application developers to toe the line by preventing them from adding their own code into the browser's components directory.

"Firefox is built around the idea of extensibility - it’s part of our soul," proclaimed Mozilla's Jonathan Nightingale in a blog post earlier this week.

"Users can install extensions that modify the way their browser looks, the way it works, or the things it’s capable of doing. Our add-ons community is an amazing part of the Mozilla ecosystem, one we work hard to grow and improve."

However, the open source browser maker has proved it isn't averse to slamming the door on rebellious coders.

Nightingale said from Firefox 3.6 onwards - including future beta releases of that iteration of the browser - it would prevent third party applications from adding code directly to the components directory.

"There are no special abilities that come from doing things this way, but there are some significant disadvantages," noted Nightingale.

He said such components are added via a stealth installation making them invisible to the user, which prevents them from being able to manage or indeed disable the extensions through the add-ons manager function.

"What’s worse, components dropped blindly into Firefox in this way don’t carry version information with them, which means that when users upgrade Firefox and these components become incompatible, there’s no way to tell Firefox to disable them," he said.

"This can lead to all kinds of unfortunate behaviour: lost functionality, performance woes, and outright crashing – often immediately on startup."

Effectively, from hereon in the components directory will be a Firefox-only playpen. Mozilla hopes this lockdown will make the browser more stable for the user. ®